Tuesday, April 22, 2014

What To Do When Canadian Tire No Longer Stocks The Part??

World Hancock 24-M-L-46 Air Motor Reverser Lever Missing
Cab Restoration CPR 4-6-4 Royal Hudson #2858 
At Canada Science & Technology Museum

A project of Bytown Railway Society's "Dirty Hands Club"

Bytown Railway Society's "Dirty Hands Club" has been restoring the cab of CPR 4-6-4 Royal Hudson #2858 at the Canada Science & Technology Museum in memory of long-time and founding member, Duncan Dufresne.  The DHC has encountered many challenges in this project, not the least of which is missing parts, parts that have rusted or corroded, or parts that no longer function.  

When parts are no longer available from commercial sources, they have to be made from scratch.  The parts can be made from standard metal bar stock using a metal lathe and a Bridgeport milling machine, or in the case of the Air motor reverser lever, cast in silicon bronze using the "lost-wax" method.  

This is but one small chapter in that restoration. 

Step 1 - Find an original.  Take Measurements.  Take Photos.  
Photos & Measurements From #2850 At Canadian Railway Museum "Exporail"

Photos of Air Motor Reverser Lever On CPR 4-6-4 #2850 at Canadian Railway Museum "Exporail"
Step 2 - Make A Wooden Pattern
There are 16 pieces of wood in this pattern. 
Wooden Pattern of Air Motor Reverser Lever Before Painting
Step 3 - Make RTV Rubber Molds From The Wooden Pattern
Making The Second Half of RTV Rubber Molds
Step 4 - Make Wax Patterns From RTV Rubber Molds For "Lost Wax" Casting
Wax Patterns Being Made.  Adding Sprues, Gates & Risers.  The Completed "Lost Wax" Tree - Ready For Ceramic Slurry.
Step 5 - Prepare Wax Patterns For Casting
Coat the "Lost Wax" tree in a slurry of ceramic shell and silica sand.  Allow the slurry to air-dry.  Repeat 8-10 times.
Fire the ceramic shell at 1700F for 30 minutes to melt out the wax and to create a ceramic mold. 
Ready For Baking.  Wax Being Melted & Shell Being Fired.  Ceramic Mold Ready For Pouring Bronze
Step 6 - Melt & Pour Bronze
Melting The Bronze - 2200F.  Pouring Molten Bronze Into Ceramic Molds
The wooden pattern was made by "Jedi Master" Ross Robinson and "Master Caster"  Bob Moore from measurements taken by John Bryant and Andy Cameron at the Canadian Railway Museum, "Railexpo", at St Constant, QC.  RTV rubber molds and wax patterns were made by Bob Moore.  Bronze castings, ceramic shells, and wax trees were made by Bronze Sculptor Dale Dunning and Ryan.   

Step 7 - Straight Out Of The Mold, Ready For Finishing
Ready For Finishing
Step 8 - Machined, Fitted, & Installed
Machined, Fitted & Installed
From Start To Finish

The "Dirty Hands Club" (a very, very informal crowd) gathers most Wednesday and Saturday mornings at the Canada Science & Tech Museum to work on the #2858 project and in the restoration of its fleet of operating rolling stock.  You can find them right in the back of the Museum complex in Building #2495.  Just follow the train tracks. 
 

Some Other Bronze Castings With Their RTV Rubber Molds

Bob Moore

Pyle Nuts - Part 3 - Pouring The Bronze

So far just a place-keeper. 

Saturday, July 20, 2013

Pyle Nuts - Part 2 - Wax Patterns & Investments

Now that we have our mold box and rubber mold made, we are ready to produce wax patterns that replicate the Pyle nut. 

Making The Wax Patterns
A trip to the grocery store and we had some paraffin wax that we could melt.  Wax should NEVER be melted by direct heat or flame!  Very hazardous!  A trip to the local Sally Ann and we picked up a rice-cooker.  For our melting pot, a tin can rescued from the recycle bin did the job.

Poured about 1" water into the rice cooker, plugged it in.  Placed a chunk of paraffin wax in the tin can, placed it in the water and let things heat up.  After 15 minutes or so, we had molten paraffin wax.  This is VERY hot so be careful!
Getting Ready For Pouring Wax

While the wax was melting, we put some duct tape over one end of the rubber mold.  A large rubber band kept the four pieces (the two mold-halves and the two mold boards) tightly together.  Just in case we had some accidents, we placed the mold assembly into a large plastic lid (from one of the DHC's large cans of Folger's coffee).

Using some angled gas pliers, we lifted the tin of molten wax out of the rice cooker and slowly poured the wax into the top of the mold. Make sure you are wearing safety glasses for this part!  Molten wax can splash. 
Pouring Wax

We let the molten wax cool for at least 30 minutes as the centre of the mold would still be liquid.  As the wax cooled, the wax in the sprue started to shrink.  This is normal as wax expands when liquid but shrinks when it turns solid.

We then removed the rubber band and slowly pried the two halves of the rubber mold apart.  Voila!  A perfect wax replica of our pattern.  Now to make a whole bunch more. 

Mounting The Wax Patterns
Now that we have our wax patterns made, we next have to mount them on a central wax sprue. 


Monday, July 8, 2013

Pyle Nuts - Part 1 - Making The Mold Box & Rubber Mold

Pyle Wing Nuts
A Pyle wing nut has two vertical half-oval-shaped wings on each side of the nut.  The centre of one wing is open.  This allows the nut to be further tightened by inserting a small bar in the hole and tighetening the nut.  The Pyle nut was used to close the lid on locomotive headlamps. 
Pattern For Pyle National Wing Nut

Our objective is to cast 6 Pyle wing nuts in bronze.  This will be done using the lost-wax or investment casting process.  The Pyle nut has been made out of wood and painted black.  Our next step is to make a mold box which will be used to make a rubber mold of the part.

Once we have the rubber mold made, we will then be able to make wax castings/patterns of the Pyle nut.   

The wax castings are then placed in a cylinder with wax sprues, gates and risers added to the wax castings.  We then pour casting plaster into the cylinder.  Once the plaster has hardened, we'll bake out the wax leaving a hollow mold that's the exact shape of our Pyle nuts.  Melt some bronze, pour it into the mold and we should have a Pyle wing nut.

So let's get started with the first two steps - making a mold box and then the rubber mold.  

1.0 Make The Mold Box
1.1 Cut - 2 pcs 4" wide x 3" high  x 3/4" thick Baltic birch. 
             - 2 pcs 2 1/2" wide x 3" high  x 3/4" thick Baltic birch.
             - 1 pc  6" wide x 6" long  x 3/4" thick Baltic birch. 

1.2 Drill holes in the two pieces 4"x 3" at ends for #8 x 1 1/2" Robertson screws.  Holes are located 3/4" from top and bottom and 3/8" in from the edge.

1.3  Loosely fit, align, assemble, clamp four pieces together in the shape of a box.

1.4 With the 4"x 3" pieces aligned, insert a 1/8" drill into the screw holes and drill holes into the edges of the two pieces of 2 1/2" x 3" about 3/4" deep.  This will prevent the plies on the 2 1/2"x 3" pieces from splitting when the pieces are screwed together. Repeat this step for all other screw holes. 

1.5 Screw the four pieces together so as to ensure a good square and level fit.

1.6 For ease of assembly, stamp the tops of each piece with identifying letters/numbers

1.7 - Mark the outline of the box on the 6"x 6" base plate.  Drill four 1/8" holes from the top in the middle of each side. 

1.8 On the bottom side, countersink the holes drilled in 1.7.

1.9 Align the box with the top of the base.  Insert a 1/8" drill into the screw holes and drill holes into the bottom edge of the four box pieces about 3/4" deep.  This will prevent the plies on the box pieces from splitting when the box is screwed to the base plate. 

The Bits-&-Pieces Of The Mold Box, Cut, Marked & Ready To Assemble

The Assembled Box & Base Plate Ready For Painting

1.10 Disassemble the four side pieces.  Paint the four side pieces and the 6"x 6" base plate with two coats of yellow paint. 

1.11  Spray all pieces with two coats of clear lacquer.  Dust talc powder  onto all pieces after the lacquer has dried. 


2.0  Making Bottom Half of Mold
2.1 Coat the insides of the side pieces and the top of the base with Vaseline.  This will  form a mold-release so that the rubber will easily release from the pattern and mold box.  Re-assemble the box to the base with the #8 x 1 1/2" Robertston screws.


2.2 Get some modelling clay from Craft Store (Wallacks, Michael's, etc). 

2.3 Place 1 1/2" of modelling clay in the bottom of the mold box.  Press the pattern into the centre of the clay up to the parting line.  Push the modelling clay flush against the parting line of the pattern with an X-Acto knife. 

2.4 Roll a 3/8" piece of modelling clay.  Cut a section of the clay in half along the radius/ centre line.  Press the half-round of modelling clay into the mold box between the ends of the pattern and the sides of the mold box and shape in place.  This will form a sprue and riser for the wax to enter the mold. 

2.5 It may be necessary to fill any gaps between the sides of the mold box so that the RTV rubber doesn't leak from the box.  Using the X-Acto knife, press modelling clay into these gaps. 

2.6 Clean excess clay off the pattern and from the sides of the mold box.  .   

2.7 Make "registration marks" in the four corners of the modelling clay.  Press the blunt end of a Sharpie marker into the modelling clay so as to create round depressions. The "registration marks" will help align the two halves of the rubber mold together. 

2.9 Apply Vaseline, oil, or grease to the sprue, riser, and registration marks.
The Mold Box & Pattern Ready For Pouring Rubber

3.0 Pour Liquid Rubber Into The Mold Box
3.1  RTV rubber is a 2-part compound - the rubber which is in liquid format, and the catalyst which, when mixed with the rubber, will result in a solid rubber mass.  There are two time elements to consider when using RTV rubber.  The first is the "open time".  This is the amount of time that the rubber can be worked with before it starts to harden.  The second time element is "demold time".  This is the amount of time required for the rubber to completely harden.  The "open time" and "demold time" will depend upon the type and manufacturer.  Refer to the manufacturer's instructions. 


3.2 The "mix ratio" of rubber to catalyst will depend upon the type of rubber being used.  Refer to the manufacturer's instructions. 


3.3  We will be using Alumilite Quick-Set Silicone Rubber.  The "open time" is 30 minutes.  The "demold time" is 8-18 hours.  The "mix ratio" of rubber to to catalyst is 10-to-1 (10:1).  That is, for every 100 grams of rubber, we will need 10 grams of catalyst.
 

3.4 Gather the tools and materials required to mix rubber:

__ RTV Rubber Kit __ Weigh Scales
__ Paper Coffee Cups (2) __ Stir Sticks
__ Paper Towels __ Mold Box
__ Garbage Pail Close By __ Rubber Gloves


Tools & Materials Required To Mix RTV Rubber

3.5 Sand one of the rounded ends of the stir sticks so that one end is flat.  This will allow the stir stick to get into the edges of the paper coffee cup when mixing the rubber and catalyst.  Using a utility knife, cut the paper coffee cups back to a height of about 2 1/2"- 3".  This will facilitate the measuring, stirring, and pouring of the liquid rubber.

3.5 We need to calculate the volume/weight of rubber required so as to provide 1" of rubber over the highest part of the pattern.  Pour water into the mold box until it is 1" above the top of the pattern.  Pour the water into a paper coffee cup and weigh the water.  For this project, the weight of the water is 100 grams and thus we will need 100 grams of liquid RTV rubber. 


3.6 Place a dry coffee cup on the weigh scale.  Using the weight scale, pour 100 grams of rubber into the cup.  Then pour the catalyst on top of the rubber until the scale reads 110 grams.  This will give us the 10:1 ratio of rubber to catalyst.

3.7 Thoroughly mix the rubber and accelerant together for 3-4 minutes.  Slowly pour the mixed rubber into the top of the mold box in a thin string so as to minimize air bubbles. DO NOT pour the rubber onto the top of the pattern. 

3.8 If you have access to a vacuum pump, remove the air bubbles from the RTV rubber.

3.9 Let rubber harden for 24 hours.     

4.0 Add Resin/Plastic "Mold Boards"
4.1 We will mix and pour a 1/4" layer of resin/ plastic on top of the rubber mold after cutting two registration marks into the hardened rubber.  This will provide support and minimize deformation of the rubber mold when we join the two halves of the rubber mold together for pouring. 

4.2  Plastic resins are a 2-part compound - the resin and the catalyst which are in liquid format.  The two, when mixed together, will result in a solid plastic.  There are two time elements to consider when using resin.  The first is the "open time".  This is the amount of time that the resin can be worked with before it starts to harden.  The second time element is "demold time".  This is the amount of time required for the resin to completely harden into a plastic.  The "open time" and "demold time" will depend upon the type and manufacturer.  Refer to the manufacturer's instructions.

3.3  We will be using Alumilite Regular Castin Resin.  The "open time" is 90 seconds.  We will have to move quickly to mix the resin and catalyst, and to pour the mix into the mold box.  The "demold time" is 8-18 hours.  The "mix ratio" of resin to catalyst is 1-to-1 (1:1).  That is, for every 100 grams of resin, we will need 100 grams of catalyst.

4.2 Using an X-Acto knife cut two V-shaped slots in the rubber mold next to the mold box.  These will serve as registration marks for the plastic mold boards. 
Rubber Mold With Registration Marks Ready For Plastic "Mold Boards"

4.4 We need to calculate the volume/weight of resin/plastic required so as to provide 1/4"" of plastic over the top of the rubber.  Pour water into the mold box until it is 1/4" above the top of the rubber.  Pour the water into a paper coffee pot and weigh the water.  For this project, the weight of the water is 50 grams.  Since our mix ratio of Resin (Part A of our Alumilite) and Catalyst (Part B of our Alumilite) is 1:1 and we need a total of 50 grams of resin/catalyst mix, we will need 25 grams of resin and 25 grams of catalyst for this project.  

4.7 Gather the materials and tools required to mix the resin::

__ Plastic Resin Kit __ Weigh Scales
__ Paper Coffee Cups (3) __ Stir Sticks
__ Paper Towels __ Mold Box
__ Garbage Pail Close By __ Rubber Gloves

4.8 Into one of the paper coffee cups, pour 25 grams of resin into one of the paper coffee cups.  Call this cup "A".  Into another paper coffee cup pour 25 grams of catalyst.  Call this cup "B".

4.9 If you want, pour 3-4 drops of dye into cup "A" and stir until the mixture is a consistent colour.  In our project we are going to use some brown dye.

4.10 Pour the contents of "A" into "B" and stir, making sure the stir stick reaches into the sides of the coffee cup.

4.11 Now pour the contents of "B" back into "A" and stir vigorously.  This will make sure that we are mixing as much of the resin and catalyst together.

4.12 Pour the mixed contents of "A" slowly into the top of the mold box.

4.13 DO NOT try to pour any of the contents of "B" into the mold box.  If dye has been added, the colour of "B" will be slightly different from the colour of "A" which will be very noticeable when the plastic sets in the mold box.  It's around this time that the plastic starts to harden and, as you pour the contents of "B" into the mold box, air bubbles may start to appear.  
Plastic "Mold Boards" Just Poured

4.14 Allow the resin to harden for 24 hours. 

5.0 Demolding The Bottom Half Of the Rubber Mold
5.1 Remove the 6"x 6" mold board from the bottom of the mold box. 

5.2 Unscrew and remove the four mold box side pieces. 

5.3 Remove the modelling clay from the pattern and the rubber.  DO NOT disturb the pattern in the rubber!

5.4 If necessary, brush off/wash away any clay remaining on the pattern and the rubber. Regrease the sides of the mold box and base with Vaseline, oil, or grease. 

5.5 With the plastic mold board flush to the bottom of the mold board, fasten the mold box sides around the rubber mold, pattern, and plastic with the #8 Roberston screws.  Screw the mold box to the 6"x 6" base with #8 Robertson screws. 

5.6 Using a full round of 3/8" diameter modelling clay from 2.4, lay the round modelling clay in the half-round channels created in 2.4 between the ends of the patterns and the sides of the mold box.  This will form a round sprue and riser for the wax to enter the mold. 

5.7 Liberally brush Vaseline/oil over the exposed pattern, modelling clay, AND rubber. 

5.8 Calculate, mix, and pour liquid rubber into the mold box following the instructions in Sectin 3.0.  Let stand for 24 hours. 

5.9 Using an X-Acto knife cut two V-shaped slots in the rubber mold next to the mold box.  These will serve as registration marks for the plastic mold boards.

5.10 Add 1/4" resin/plastic "mold board" on top of the solid rubber following the instruction in Section 4 AFTER cutting the two registration marks in 5.9.  

5.11 Remove the mold box and base plate from around the rubber mold. 

5.12 Separate the two halves of the rubber mold.  Remove the pattern and modelling clay from the rubber mold. 

5.13 Carefully trim excess rubber from the sides of the mold. 

5.14 Reassemble the two halves of the rubber mold aligning the halves with the registration marks.  Tape the two halves together. 

5.15 The rubber mold is now ready for pouring molten wax into the mold.
The Finished Rubber Mold Ready For "Waxing"

Next up, we make some wax patterns and encase the patterns in some casting plaster.  

Monday, February 13, 2012

Marker Lantern Brackets - The Final Product

In our previous post we chronicled one of the last days at Imbleau's Iron Foundry in Renfrew.  Their last pour was on the following Tuesday, February 7th, 2012.

Our post prior to that were a set of instructions for making the green sand mold to pour the corner lantern brackets.  Here's what the casting looked like about an hour after the molten iron had been poured into the mold at Imbleau's.
In case you're having difficulty seeing where the casting is, here's another photo with some added captions.
Here's a photo of another one of the brackets.
The steam is still rising from the green sand and the castings are still very, very hot.  Don't touch!!

Just to recap on the process, we started off with an original casting that we had to duplicate.  The hollows and holes were filled in by Jedi Master Ross producing the following pattern.
We next had to make a sand core to produce the holes and hollows that we had just filled up. So, Jedi Master Ross made a core box so that we could make sand cores.  After a few modifications, we were able to start production of the sand cores.
Which, as you can visualize from the photo below, would nicely create the hollow that we need in the mold.
From there, we went on to make a dozen sand cores for our 12 castings - 6 for the flat lantern brackets and 6 for the corner lantern brackets.
One thing I learned with the first castings that I had done at Alumaloy was to test the sand cores and make sure that they fitted snugly into the green sand mold.
With the sand cores tested, we took our first batch up to Imbleau's for casting.  Here's the pattern ready to go along with the 6 sand cores.
These were cast on Friday, January 27th.  This is what the castings look like.  The sprue, gate, and risers have been knocked off and you can still see the sand cores in the middle of the casting.
It was then that we discovered a challenge facing us.  I had originally though that I could simply soak the casting in water and the sand core would disintegrate.  So much for that idea!  It took 15 minutes to sand-blast the sand core out of each casting.  This is what the lot looks like with the sand cores removed and a bit more of the "flash" knocked off with a chipping hammer.  Each one of those castings is a solid block of iron! 
I was completely surprised that we were able to get things along this far!  I was expecting an unrecognizable  blob of iron. 

Of course, the fun had only just started.  First step was to drill out the holes for the mounting screws.  While most of the 24 holes (6 castings x 4 holes per casting = 24 holes), there were 4 holes that wouldn't centre.  A bit of grinding with a Dremel solved that problem.

Next up was to grind off the flash and the rough spots.  One thing I discovered was that the sand cores were a bit loose in the green sand mold with the result that we had an extra bit of iron in the flash.  Next time, we'll have to make the sand cores so that there is a tighter fit.  Oh well, that's one lesson learned, eh!?

And this is what the final product looks like before Master Painter Charls gave them three coats of paint.

Not bad for a bunch of amateurs, eh!?

Thursday, February 2, 2012

A Day At Imbleau's Foundry - The Last Pour

I took a trip up to Renfrew today to pick up the patterns and castings that I had dropped off last Thursday and to see the pouring for the patterns that I had dropped off on Friday.  Today was going to be a sad day as this was the last day that Imbleau's, after 160 years, would be pouring iron. 

When I arrived, molten iron was running continuously from the foundry into the large crucible.

From there, each worker would place their smaller crucible on the ground.  The foundryman would then tip the large crucible and red-hot molten iron would pour into their crucible. 

A large crucible suspended on a travelling crane was placed near this part of the operation and the workers would empty the molten iron into the larger crucible.  Three workers would then manouver the large crucible into the rows of large sand molds and align the lip of the crucible until it was exactly into the right position to pour the molten iron in the sprue of the sand mold.  The crucible was slowly tipped forward and molten iron poured into the mold. 
While the pouring was going on from the large crucible, other workers would get their hand-held crucible charged with molten iron and then walk Popeye-like with the handle of the crucible resting on the top of their leg over to the smaller sand molds and pour the red-hot molten iron into the top of the sprue. 
When the iron appeared at the top of the riser, the mold was full of red-hot molten iron.  The heat from the iron immediately turned the moist sand mold into a bath of steam.  Throughout the foundry, steam was rising up into the air clouding the busy workers with their crucibles full of molten iron.   
Through the rising steam I could barely make out the workers with the large crucible pouring the large sand castings. 
Each worker seemed to automatically know what to do.  There were no orders being shouted out by the foremen.  They all worked in unison.  When the large crucible was moved over to the furnace, a semi-circle of workers would form.  As their small crucible was filled, they would move to the other side of the circle and pour it into the large crucible, taking their place at the end of the line once again. 
When the large crucible was filled, three workers would move it away from the furnace and the other workers would then get their smaller crucibles filled with molten iron.  One worker would go off into the south-eastern corner of the building; another worker would go off into the north-western part, each one followed by another worker who prepared the sand molds for pouring - lift the weight off of the molds that had been poured, shove a flask over the mold, then place the weight on top of the mold.  Right behind him was the worker with the molten iron. 
As the pour was coming to an end, the workers not pouring molten iron would up-end the sand molds to expose the iron castings.  This would allow them to cool off faster.  The molds were up-ended into rows where the green sand would be reconditioned for the next molding session. 
I peered into the steaming cauldron of black sand seeing if I could see my castings.  Aha!!  There at the end of the row was one of my corner brackets. 
Finally, the last of the sand molds was filled with molten iron.  It was now time to pull the plug on the foundry to empty it of the molten and unmelted iron that was mixed in with the red-hot and unburnt coke.  The wire rope was pulled, the furnace doors opened at the bottom and a large roar of flame shot up to the ceiling as the whole contents of the furnace dropped to the ground. 
Anyone standing in front of that inferno would have been cooked to a crisp. The flame settled down and one of the workers hosed a steady flow of water onto the fiery mass. 
Hard to understand the significance of that fiery flame as the contents of the furnace dropped to the ground.  It signalled the end of an era that had lasted for more than 160 years. 

Monday, January 30, 2012

Marker Lantern Corner Brackets - Steps For Making Sand Molds

The pattern for the Marker Lantern Corner Brackets consists of the following elements:
  1. Main Pattern (painted black with yellow core prints)
  2. "False pattern" (painted blue)
  3. "False core print" (unpainted)
  4. Wing-nut bolt (painted blue)
  5. Main sand core (irregular shape)
  6. Wedge-shaped core print (Loose triangle-shaped piece of wood with the top chopped off)

The following are the suggested steps for creating the green sand mold:

1) Place the blue false pattern face down on the drag. 

2) Place the black-and-yellow main pattern on top of the blue false pattern

3) Fill and ram, etc the drag with green sand. 

4) Turn the drag over to expose the top of the blue false pattern

5) Using the two screws provided, remove the blue false pattern from the drag. 

6) Depending on the height of the alignment pins in the drag, the clearances between the cope and the drag may be very close.  In order to allow for a better clearance, cut a triangular piece out of the drag as shown in the photo below. 

7) Place the unpainted wedge-shaped core print into the drag on top of the exposed yellow core print

8) Place the cope on the drag.  Fill and ram, etc the cope with green sand. 
9) Lift cope off of the drag.  Cut in sprues, gates, risers, etc.

10) Rap and lift out the unpainted wedge-shaped core print. 

11) Insert the blue wing-nut bolt into the threaded hole in the bottom of the yellow-and-black main pattern. 

12) Rap and remove the yellow-and-black main pattern.

13) Finish off the rest of the mold, etc.   

14) Insert the main sand core

15) Insert the wedge-shaped sand core

16 Finish off the rest of the mold, etc